Tuesday, May 29, 2012
Iwo Eleru Is Not the 2% Archaic Content in Africans, but a neanderthal Hybrid
Since the discovery of mankind's Neanderthal and Denisovan ancestry, it has also been discovered that some Africans get as much as 2% of their DNA from an Archaic source other than Neanderthals and Denisovans.
Discoveries in Iwo Eleru of two "archaic" skulls that are dated around 13000 years ago have led some to dub the African admixture with the name "Iwo Eleru."
However, the culture that produced the Iwo Eleru skulls is definitely NOT the culture that contributed the 2% archaic genes. Here's why:
The 2% archaic admixture in Africa comes from a race that separated from our line over 700,000 years ago.
The Iwo Eleru skulls have been classified by numerous tests as being "half-way" between archaic (neanderthal, heidelberg, erectus, and archaic moderns from Israel) and modern humans. They are more "primitive" than any moderns known from Africa, but still less "primitive" than any archaic form of man. A race that dropped off the family tree 700,000 years ago anywhere even near Africa could only be Heidelbergensis (defined here as those who shared our common ancestor BEFORE the neanderthal split and AFTER the erectus/ergaster split) or a race of or related to Homo ergaster/antecedent (home erectus, as defined here, was only in Asia at the time).
Here are the clues that tell us what Iwo Eleru was:
* Nigerians have the most neanderthal blood in Africa.
* Iwo Eleru is in Nigeria
* Iwo Eleru skulls are the closest of any African skulls to skulls circa 120,000 to 80,000 BP, and these skulls are often cited as examples of early modern/neanderthal hybridization.
* The 2% archaic admixture in Africans is concentrated the highest in the pygmies of central Africa, not Nigerians
* No study has yet compared the Iwo Eleru skulls with the Ibero-maurusian skulls of North Africa, which are often said to be neanderthal/human hybrids.
* Ibero-maurusians practiced tooth-knocking, which is still practice among Nigerian tribes today.
* Ibero-maurusians appear in North Africa just after the last known neanderthals and neanderthal hybrids disappear from the fossil record in Europe...right across the Straight of Gibraltar from them in Southern Iberia.
* Morroccans, Egyptians, and Tunisians (North Africans) have the second largest amount of Neanderthal blood. The Ibero Marusians were invaded by the Capsians from the Middle East around 10,000 BC...roughly the same time as the dating of the Iwo Eleru Skulls.
It IS likely that the Iwo Eleru skulls ARE more primitive than those of the Ibero--maurusian specimens, and that would be consistent with this theory as well. If there were a population of modern humans living in west and central Africa up until the end of the last Ice Age, with a high degree of archaic genes (and some degree of archaic traits, but whose anatomy falls within the range of modern variation), then mixing with hybrid Ibero-maurusian invaders would indeed pronounce the resulting people's display of archaic features. As we can see from other late finds in Africa that show archaic traits, though much less extreme than Iwo Lereru, this was indeed the case. Admixture with neanderthal hybrids would also dilute the percentage of 700,000 year old genes in the Nigerian population...which might be why Nigerians have less "heidelberg" genes than bushmen, but more neanderthal genes than anyone else in Africa.
It would be interesting to compare the genes of Berbers, Nigerians, Basques, and Gaunches as it pertains to these ideas...
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2 comments:
out-of-Africa as a replacement model is finished, any way you cut it. Modern man is from the atlantic, entered Africa 35K ago and that's when you had the transgression with the archaic species. Modern man is from atlantis, not Africa. He also mated with Neanderthal in Europe, the modern type being Cro magnon, the Atlantean.
" However, the culture that produced the Iwo Eleru skulls is definitely NOT the culture that contributed the 2% archaic genes. Here's why: The 2% archaic admixture in Africa comes from a race that separated from our line over 700,000 years ago. "
The reason that they were halfway/early-sapiens like doesn't warrant a "definitely not". Morphology doesn't necessarily follow genetics proportionally, and both are also not aligned in a clear chronological fashion.
One could even argue that there's no actual "archaic admixture" in Africa (or even elsewhere) at all, at least not something to be understood as admixture between populations of markedly different aspects of "modernity", that were separated at the population level for long periods.
Simply because genes have their own genealogies/lineages, and aren't all fixed/at 100% frequency in all the population, you can have old genetic divergences within the same population, and the maintenance of such relics can be aided with the isolation of populations of the same/closer morphology (closer than the modern-archaic difference).
I think it's quite inappropriate to title a paper with "genetic evidence for archaic admixture" when you show is only a model that explains the data as archaic admixture, not actual archaic genomes to compare as "genetic evidence". It's basically the same issue with an earlier paper which posited late hybridization with chimpanzees to explain some archaic-ness of the human X chromosome, also titled "genetic evidence" for complex speciation. It may look like, and may even be the case, but the model isn't itself evidence, as there's alternative models that give a different explanation to the same data. All you got to do is to have different assumptions for population sizes, structures, bottlenecks.
The other great primates have a much higher divergence than humans do (which incidentally reaffirms the non-1:1 correspondence of genetic divergence and phenotypic). If you look at phylogenetic trees you'll see that all living humans are so close as a tiny fraction of chimps, and that the entire chimp variation is like 2 or 3 times larger than the variation of MH+neanderthals+denisova.
As humans share a common ancestor with these species, it's only natural to expect that our past variation was also more dramatically divergent. We progressively became less divergent with the combination of increased panmixy and bottlenecks. Remnants, genetic lineages, of this past higher genetic distances would still be seen at higher levels, specially in Africa, but would also possibly explain apparent neanderthal and denisova "admixture", specially if we're allowed to postulate other sorts of intermediate/alternative scenarios between multiregional evolution and recent replacement.
I'm not saying that archaic admixture didn't happen, nor that Iwo Eleru people couldn't have been sapiens+neanderthal hybrids. Just ranting against the internets, which I shouldn't really do.
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